There is growing evidence that new neurons are generated in the hippocampus of adult animals throughout life and it has been hypothesized that hippocampal neurogenesis plays a critical role in memory function. Memory is an important component of mental health and thus it is crucial to understand regulation of neurogenesis. The proposed study will investigate the relationship between environmental complexity and hippocampal plasticity in food-caching birds. Enriched environment appears to induce adult neurogenesis but it is not clear which specific aspects of environment are responsible for facilitating neurogenesis. In addition, all experiments investigating environmental enrichment have been done in laboratory conditions, which are always poor compared to natural environment. This study will investigate whether natural memory-based experiences are necessary to maintain hippocampal structure and whether lack of such experiences results in reduced hippocampal volume, loss of hippocampal neurons and reduced neurogenesis using a novel animal model - food-caching birds. Food-caching birds are heavily dependent on memory to find previously made food caches and cache-recovery behavior presents a great natural model to study memory and the brain both in controlled laboratory and natural conditions. Birds living in natural conditions will be compared to the birds maintained in standard and in enriched laboratory conditions to establish whether hippocampal neurogenesis in enriched laboratory conditions is comparable to that in animals living in natural environments. The overall aim of this proposal is to evaluate the relationships between natural memory-based experiences and the hippocampus both in laboratory and in natural conditions using a novel animal model. This study will provide new information on the effects of memory exercise on the hippocampal structure and neurogenesis, which have important implications for memory and mental health. The proposed study will investigate whether exercising memory is necessary for maintaining healthy memory and the hippocampus, an area of the brain involved in memory function and whether diverse environment is needed for brain maintenance. Memory is an important aspect of mental health and the proposed research will provide new insights into better understanding of human memory disorders. [unreadable] [unreadable] [unreadable]